Employers are increasingly making CSCS (Construction Skills Certification Scheme) cards mandatory to enable you to work on a construction site. This ensures that the site complies with current health & safety practices that affect workers so they understand and adhere to these. You should also be aware that firstly, regular checks are carried out on CSCS card holders either by using a hand held scanner or checking a central database to ensure the card is valid. Secondly, if you are holding the wrong type for the type of job you are doing, for example, if you have a CSCS Green card but you are of card in fact a painter, plasterer or supervisor, you might be asked to leave the site.